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Open Access Publications from the University of California

Hydrogen evolution activity of individual mono-, bi-, and few-layer MoS2towards photocatalysis

  • Author(s): Parzinger, E
  • Mitterreiter, E
  • Stelzer, M
  • Kreupl, F
  • Ager, JW
  • Holleitner, AW
  • Wurstbauer, U
  • et al.

© 2017 Elsevier Ltd We investigate the hydrogen evolution activity in the dark and under illumination above the band gap of individual mono-, bi- and few-layer (bulk) MoS2flakes. We demonstrate that the electrocatalytic activity of 2H-MoS2immersed in 1 M H2SO4increases with decreasing number of layers. For monolayers, we observe the highest exchange current density, which is one magnitude larger than in the bulk case. The onset potential scales with the number of layers, which is consistent with a previous report, suggesting that hopping transport across inter-layer barriers within the MoS2flakes is responsible for this scaling. A specially designed micro-sized catalytic cell enables us to investigate individual MoS2flakes with well-known geometry and edge-to-surface ratio. Taking these geometric parameters into account, we tentatively attribute the catalytic activity mainly to sulfur vacancies in the basal planes acting as active sites. The associated turn over frequencies (TOF) for mono- and bi-layer MoS2yield values higher than 103s−1at an overpotential of −0.2 V vs. RHE. In view of light driven hydrogen evolution as a means of solar energy conversion, we investigate the photocatalytic activity of few-layer MoS2under white light illumination.

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